This invention relates in general to safety devices for vehicles and, in particular, to a locking device for use with the transmission of a self-propelled vehicle. More specifically, but without restriction to the particular use which is shown and described, this invention relates to a restriction latch device that prevents a transmission gear shift lever of a vehicle from accidentally or inadvertently being placed into a neutral position that permits the vehicle to be moved from one location to another.
Self-propelled vehicles, such as construction machinery and earth moving vehicles, utilize a transmission to couple the output of the vehicle engine to a drive system. The transmission is manually operated by the vehicle operator by moving a transmission or gear shift lever which is freely moveable through various positions to change the output of the transmission. Such transmissions have a gear shift pattern which describes a physical layout of the various positions that the gear shift lever can move through in order to change the output from the transmission. Generally, the gear shift pattern has positions which correspond to the drive gears of the vehicle, i.e., forward and reverse, and a position corresponding to the transmission being in neutral.
Certain types of construction machinery require two gear shift positions when the vehicle transmission is in neutral. One gear shift position corresponds to a "BRAKES ON" position wherein the vehicle transmission is in neutral, but the brakes are applied to prevent any movement. Normally, when these vehicles are being started the transmission gear shift lever is placed into this "BRAKES ON" position in the gear shift pattern. For safety this allows the vehicle to be started while the brakes are locked. The other neutral position is a "BRAKES OFF" position, wherein the vehicle transmission is in neutral, but the brakes are not applied. This position allows the vehicle to be moved, such as when the vehicle is to be loaded onto another vehicle for transport to a job site. By placing the gear shift lever into the "BRAKES OFF" neutral position, the vehicle can be easily towed or pushed by another vehicle to a desired location.
Due to space limitations imposed by the vehicle transmission, the "BRAKES OFF" and "BRAKES ON" positions are in close proximity. Therefore, the vehicle operator might unintentionally shift the transmission into the "BRAKES OFF" position when intending that the vehicle be shifted into the "BRAKES ON" position which could cause damage and/or bodily injury. To eliminate the potential hazard which might occur in the event that the vehicle operator unintentionally or accidentally placed the transmission gear shift lever into the "BRAKES OFF" position, the present invention prevents the gear shift lever from being inadvertently placed into this position.
The invention utilizes a spring-biased restriction latch to prevent the gear shift lever from being accidentally or unintentionally put into the "BRAKES OFF" position. In order for the vehicle operator to move the gear shift lever into the "BRAKES OFF" position, the operator must first manually rotate a release latch into a position in which it is no longer a physical barrier for the gear shift lever. The gear shift lever can be then shifted into the "BRAKES OFF" position. Upon release by the operator, the release latch, being spring biased, will move to a closed position.
When the vehicle operator then wishes to move the gear shift lever from the "BRAKES OFF" position, the operator merely moves the gear shift lever into contact with the release latch and it can be rotated into an open position. The operator can then freely move the gear shift lever from the "BRAKES OFF" position to any desired gear position. The release latch will again be spring biased back into its original position setting up the physical barrier to prevent the gear shift lever from being inadvertently placed back into the "BRAKES OFF" position.